Due to an improving economy and more competition among credit card issuers, card holders with good credit are being rewarded with lower interest rates and more generous sign-up bonuses, according to a new report from CardHub.com. For those with the best credit, the average interest rate was 12.79 percent in the first three months of 2013, down 1.69 percent from the last quarter of 2012. At the same time, however, rates for cardholders with the weakest credit are on the rise; and interest for those with "fair credit" is up 3 percent. The average length of a 0 percent introductory rate for balance transfers for strong-credit customers increased in the first quarter to 10.29 months, 2.39 percent longer than in the fourth quarter of last year. Their average cash-back initial bonus was $76.81 in the first quarter, up 15.4 percent over the previous three months. As delinquency and unemployment rates have stabilized, card issuers have been able to pass savings to the best customers.